Internal combustion engines (ICE) are often called upon to generate considerable levels of power for prolonged periods of time on a dependable basis. Many such ICE assemblies employ a supercharging device, such as an exhaust gas turbine driven turbocharger, to compress the airflow before it enters the intake manifold of the engine in order to increase power and efficiency.
Specifically, a turbocharger is a centrifugal gas compressor that forces more air and, thus, more oxygen into the combustion chambers of the ICE than is otherwise achievable with ambient atmospheric pressure. The additional mass of oxygen-containing air that is forced into the ICE improves the engine's volumetric efficiency, allowing it to burn more fuel in a given cycle, and thereby produce more power.
In an effort to increase overall engine efficiency and response, some ICE's employ two-stage turbocharging systems which include a smaller turbocharger driven by lower exhaust flows and a larger turbocharger driven by higher exhaust flows. A transition between the two turbochargers in such a two-stage system is typically controlled based on the particular engine's configuration and operating requirements.
At higher engine speeds and loads, temperatures of engine exhaust gas generally become elevated. As a result, turbochargers frequently experience substantial thermal stresses that may require implementation of structural reinforcements and high-temperature materials to ensure reliable turbocharger operation.